The W+W- and ZZ production cross sections are measured in proton-proton collisions at sqrt(s) = 8 TeV with the CMS experiment at the LHC in data samples corresponding to an integrated luminosity of up to 5.3 inverse femtobarns. The measurements are performed in the leptonic decay modes W+W- to l' nu l'' nu and ZZ to 2l 2l', where l = e, mu and l'(l'') = e, mu, tau. The measured cross sections sigma(pp to W+W-) = 69.9 +/- 2.8 (stat.) +/- 5.6 (syst.) +/- 3.1 (lumi.) pb and sigma(pp to ZZ) = 8.4 +/- 1.0 (stat.) +/- 0.7 (syst.) +/- 0.4 (lumi.) pb, for both Z bosons produced in the mass region 60 < m[Z] < 120 GeV, are consistent with standard model predictions. These are the first measurements of the diboson production cross sections at sqrt(s) = 8 TeV.
The measured cross section for W+ W- production performed in the W --> LEPTONPRIME NU mode where LEPTONPRIME is electron, muon or tau.
The measured cross section for Z0Z0 production performed in the Z0 --> LEPTON LEPTONPRIME mode where LEPTON is E or MU and LEPTONPRIME is E, MU or TAU.
The reaction gamma + p -> K+ + Sigma + pi was used to determine the invariant mass distributions or "line shapes" of the Sigma+ pi-, Sigma- pi+ and Sigma0 pi0 final states, from threshold at 1328 MeV/c^2 through the mass range of the Lambda(1405) and the Lambda(1520). The measurements were made with the CLAS system at Jefferson Lab using tagged real photons, for center-of-mass energies 1.95 < W < 2.85 GeV. The three mass distributions differ strongly in the vicinity of the I=0 \Lambda(1405), indicating the presence of substantial I=1 strength in the reaction. Background contributions to the data from the Sigma0(1385) and from K^* Sigma production were studied and shown to have negligible influence. To separate the isospin amplitudes, Breit-Wigner model fits were made that included channel-coupling distortions due to the NKbar threshold. A best fit to all the data was obtained after including a phenomenological I=1, J^P = 1/2^- amplitude with a centroid at 1394\pm20 MeV/c^2 and a second I=1 amplitude at 1413\pm10 MeV/c^2. The centroid of the I=0 Lambda(1405) strength was found at the Sigma pi threshold, with the observed shape determined largely by channel-coupling, leading to an apparent overall peak near 1405 MeV/c^2.
Invariant mass distributions of the three SIGMA-PI combinations for centre-of-mass energies, W, from 1.95 to 2.05 GeV corresponding to incident photon energies from 1.56 to 1.77 GeV.
Invariant mass distributions of the three SIGMA-PI combinations for centre-of-mass energies, W, from 2.05 to 2.15 GeV corresponding to incident photon energies from 1.77 to 1.99 GeV.
Invariant mass distributions of the three SIGMA-PI combinations for centre-of-mass energies, W, from 2.15 to 2.25 GeV corresponding to incident photon energies from 1.99 to 2.23 GeV.
At the LHC energy of $\sqrt s = 7\,{\mathrm { TeV}}$ , under various beam and background conditions, luminosities, and Roman Pot positions, TOTEM has measured the differential cross-section for proton-proton elastic scattering as a function of the four-momentum transfer squared t. The results of the different analyses are in excellent agreement demonstrating no sizeable dependence on the beam conditions. Due to the very close approach of the Roman Pot detectors to the beam center (≈5σ(beam)) in a dedicated run with β* = 90 m, |t|-values down to 5·10(−)(3) GeV(2) were reached. The exponential slope of the differential elastic cross-section in this newly explored |t|-region remained unchanged and thus an exponential fit with only one constant B = (19.9 ± 0.3) GeV(−)(2) over the large |t|-range from 0.005 to 0.2 GeV(2) describes the differential distribution well. The high precision of the measurement and the large fit range lead to an error on the slope parameter B which is remarkably small compared to previous experiments. It allows a precise extrapolation over the non-visible cross-section (only 9%) to t = 0. With the luminosity from CMS, the elastic cross-section was determined to be (25.4 ± 1.1) mb, and using in addition the optical theorem, the total pp cross-section was derived to be (98.6 ± 2.2) mb. For model comparisons the t-distributions are tabulated including the large |t|-range of the previous measurement (TOTEM Collaboration (Antchev G. et al), EPL, 95 (2011) 41001).
The measured differential elastic cross section.
The measured differential elastic cross section in the high |T| region. where it originally appeared as a plot, but was not tabulated.
The fitted slope parameter for the elastic cross section fitted over 4 |T| ranges.
The energy flow created in pp collisions at is studied within the pseudorapidity range 1.9<η<4.9 with data collected by the LHCb experiment. The measurements are performed for inclusive minimum-bias interactions, hard scattering processes and events with an enhanced or suppressed diffractive contribution. The results are compared to predictions given by Pythia-based and cosmic-ray event generators, which provide different models of soft hadronic interactions.
Charged energy flow for inclusive mininum bias events, requiring at least one charged particle in the pseudorapidity range 1.9 < eta < 4.9.
Charged energy flow for hard scattering events, requiring at least one charged particle with transverse momentum > 3 GeV and in the pseudorapidity range 1.9 < eta < 4.9.
Charged energy flow for diffractive enriched events, requiring no charged particles in the pseudorapidity range -3.5 < eta < -1.5 and at least one charged particle in the pseudorapidity range 1.9 < eta < 4.9.
A search has been performed for the experimental signature of an isolated photon with high transverse momentum, at least one jet identified as originating from a bottom quark, and high missing transverse momentum. Such a final state may originate from supersymmetric models with gauge-mediated supersymmetry breaking in events in which one of a pair of higgsino-like neutralinos decays into a photon and a gravitino while the other decays into a Higgs boson and a gravitino. The search is performed using the full dataset of 7 TeV proton-proton collisions recorded with the ATLAS detector at the LHC in 2011, corresponding to an integrated luminosity of 4.7 fb-1. A total of 7 candidate events are observed while 7.5 pm 2.2 events are expected from the Standard Model background. The results of the search are interpreted in the context of general gauge mediation to exclude certain regions of a benchmark plane for higgsino-like neutralino production.
Missing ET distribution.
Signal Point Information: (1) Number of Monte Carlo events generated (2) Total signal cross section (pb) (3) Signal acceptance (4) Relative uncertainty on acceptance (5) CLs expected (6) CLs observed.
The observed limit contour in the GLUINO-NEUTRALINO plane.
A search for new phenomena in final states with four or more leptons (electrons or muons) is presented. The analysis is based on 4.7 fb^-1 of sqrt(s) = 7 TeV proton-proton collisions delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in two signal regions: one that requires moderate values of missing transverse momentum and another that requires large effective mass. The results are interpreted in a simplified model of R-parity-violating supersymmetry in which a 95% CL exclusion region is set for charged wino masses up to 540 GeV. In an R-parity-violating MSUGRA/CMSSM model, values of m_1/2 up to 820 GeV are excluded for 10
The transverse momentum distribution of the leading lepton for events with at least 4 leptons and no Z-boson candidate.
The transverse momentum distribution of the sub-leading lepton for events with at least 4 leptons and no Z-boson candidate.
The transverse momentum distribution of the 3rd-leading lepton for events with at least 4 leptons and no Z-boson candidate.
A measurement of the inclusive WW+WZ diboson production cross section in proton-proton collisions is reported, based on events containing a leptonically decaying W boson and exactly two jets. The data sample, collected at sqrt(s) = 7 TeV with the CMS detector at the LHC, corresponds to an integrated luminosity of 5.0 inverse femtobarns. The measured value of the sum of the inclusive WW and WZ cross sections is sigma(pp to WW+WZ) = 68.9 +/- 8.7 (stat.) +/- 9.7 (syst.) +/- 1.5 (lum.) pb, consistent with the standard model prediction of 65.6 +/- 2.2 pb. This is the first measurement of WW+WZ production in pp collisions using this signature. No evidence for anomalous triple gauge couplings is found and upper limits are set on their magnitudes.
Integrated cross section for inclusive WW + WZ production from the electron and muon channels combined.
A search for supersymmetry (SUSY) in events with large missing transverse momentum, jets, and at least one hadronically decaying tau lepton, with zero or one additional light lepton (e/mu), has been performed using 4.7 fb-1 of proton-proton collision data at sqrt(s) = 7 TeV recorded with the ATLAS detector at the Large Hadron Collider. No excess above the Standard Model background expectation is observed and a 95% confidence level visible cross-section upper limit for new phenomena is set. In the framework of gauge-mediated SUSY-breaking models, lower limits on the mass scale Lambda are set at 54 TeV in the regions where the stau is the next-to-lightest SUSY particle (tan(beta) > 20). These limits provide the most stringent tests to date of GMSB models in a large part of the parameter space considered.
The observed number of signal events as a function of Lambda and Tan(Beta).
The Acceptance, Efficiency and Acceptance x Efficiency for the single tau channel as a function of Lambda and Tan(Beta).
The Acceptance, Efficiency and Acceptance x Efficiency for the two tau channel as a function of Lambda and Tan(Beta).
High precision measurements of the form factors of proton, pion, and kaon for timelike momentum transfers of |Q^2|=s=14.2 and 17.4 GeV^2 have been made. Data taken with the CLEO-c detector at sqrt(s)=3.772 GeV and 4.170 GeV, with integrated luminosities of 805 pb^-1 and 586 pb^-1, respectively, have been used to study $e^+e^-$ annihilations into pi+pi-, K+K^-, and ppbar. The perturbative QCD prediction that at large Q^2 the quantity Q^2F(Q^2) for vector mesons is nearly constant, and varies only weakly as the strong coupling constant alpha_S(Q^2) is confirmed for both pions and kaons. In contrast, a significant difference is observed between the values of the corresponding pQCD suggested near-constant quantity, |Q^4|G_M(|Q^2|)/mu_p for protons at |Q^2|=14.2 GeV^2 and 17.4 GeV^2. The results suggest the constancy of |Q^2|G_M(|Q^2|)/mu_p, instead.
Born cross section of $e^+e^-\rightarrow h^+h^-$
Timelike form factor
Using the internal beam of DESY elastic electron-proton cross-sections were measured at various angles between 32° and 130°, and with momentum transfers ofq 2=39, 60, 80 and 110 fm−2. Two single-quadrupole spectrometers, movable around a common liquid-hydrogen target, were used for analysing the momentum of the scattered electrons. Čerenkov and shower counters discriminated against pion and low-energy background. As a cross-section reference, recoil protons from elastic scattering atq 2=10 fm−2 were used, with a quantameter serving as an intermediate monitor. The data are consistent with the Rosenbluth formula, giving real form factorsG E andG M . Both continue to decrease with increasing momentum transfer, but somewhat faster than indicated by measurements performed so far.
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